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Thread: Fuel Restrictor

  1. #1

    Fuel Restrictor

    Just want to make sure I've got this right. On my 95 SLT 750, If I run the triple outlet mikuni (pentagon) fuel pump, the 65 liter per hour version, do I still need the fuel restrictor or is that over kill ?? I can't find anything that shows a restrictor with this pump


  2. #2
    BlueFishCrisis's Avatar
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    Quote Originally Posted by cejay825 View Post
    Just want to make sure I've got this right. On my 95 SLT 750, If I run the triple outlet mikuni (pentagon) fuel pump, the 65 liter per hour version, do I still need the fuel restrictor or is that over kill ?? I can't find anything that shows a restrictor with this pump
    The restrictor has nothing to do with the pump. You need the restrictor.

    Also, if you are buying a used Pentagon pump, you should get a rebuild kit for it as well. If you are buying it new, make sure it is the three outlet version. I believe the aftermarket Pentagon pump from Mikuni is only a 2 outlet......

  3. #3
    Yes its the triple out version, new. From what I've read the restrictor has everything to do with the pump. The restrictor is what made up for the inadequate factory fuel pump, right? If both the 95 750 and 96 and up 780s have internal carb restrictors, then why doesn't the 96 and up 780s have an external restrictor.....

  4. #4
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    Quote Originally Posted by cejay825 View Post
    Yes its the triple out version, new. From what I've read the restrictor has everything to do with the pump. The restrictor is what made up for the inadequate factory fuel pump, right? If both the 95 750 and 96 and up 780s have internal carb restrictors, then why doesn't the 96 and up 780s have an external restrictor.....
    The restrictor is in place to keep pressure at the carbs and to keep fuel from simply bypassing the carbs and returning to the tank. The fuel would have the tendency to bypass the carbs and take the path of least resistance regardless of the output of the pump. The internal restrictors can be found on all 780 Fuji carbs (black), negating the need for an external restrictor. The 650 and 750 Fuji carbs (blue) regardless of year do not have the internal restrictor, and still need the external in line restrictor for proper operation.

    I may be wrong, so hopefully one of the pros will confirm or destroy my statments above.....

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    BlueFishCrisis's Avatar
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    Quote Originally Posted by cejay825 View Post
    x
    These are the new Mikuni Fuel pumps:

    http://www.mikuni.com/c-fuel_pumps.html

  7. #7
    Blue you are exactly right, although I am not a pro I understand this for sure. Maybe I can put this another way.

    Say your shooting water down a PVC pipe with each end open, it will go straight out which how your fuel system works because at the other end of your carb rack there is a return line that dumps right back in to your tank. Now lets say you take that PVC pipe and make 3 holes in the side of it and install 3 more pipes on the side. If you if your shoot water down the pipe ( your fuel in line) it will still go right out the other end (return line) of course some will get in the 3 pipes you installed but not much.

    The restrictor is there to stop us pressure inside the pipe to redirect it in to the other 3 pipes. The newer carbs have the same restrictor installed, Polaris simply said, "hey why make this harder than it has to be" and made it in to the last carb instead of having this little piece of metal you have to jam in to the fuel line.

    So in closing to clarify, there has always been a retstricor, on some years it is actually on the fuel block built in, and on someyears it is a little thing you have to jam in the line. Good luck with your ski!

    I hope that helped.

  8. #8
    Click image for larger version. 

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ID:	271267 <----------That is what all of your lines look like and so do mine except the very front one.

    Click image for larger version. 

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ID:	271268 <--- this is my return line off the front carb. You cant really see it in the picture because it is so small but that is my restrictor.

  9. #9
    Quote Originally Posted by BlueFishCrisis View Post
    The restrictor is in place to keep pressure at the carbs and to keep fuel from simply bypassing the carbs and returning to the tank. The fuel would have the tendency to bypass the carbs and take the path of least resistance regardless of the output of the pump. The internal restrictors can be found on all 780 Fuji carbs (black), negating the need for an external restrictor. The 650 and 750 Fuji carbs (blue) regardless of year do not have the internal restrictor, and still need the external in line restrictor for proper operation.

    I may be wrong, so hopefully one of the pros will confirm or destroy my statments above.....
    Yes, I'm aware of the fuild dynamics you just explained but I think the blue carbs have a restrictor also:
    From Polaris PWC Knowledge;

    Some 650 and 750 Fuji engine models have a small metal flow restrictor (Polaris part number 5020773) inserted inside the return fuel line, about one inch from the last carburetor. It looks like a brass plug in the return fuel line, and it has a tiny hole driller through the center. The restrictor is used to boost fuel pressure inside the carburetors, and is in addition to the internal flow restriction in the Mikuni SBN carburetor.

    Nothing like in field testing, thanks for the help though.

  10. #10
    BlueFishCrisis's Avatar
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    Quote Originally Posted by cejay825 View Post
    Yes, I'm aware of the fuild dynamics you just explained but I think the blue carbs have a restrictor also:
    From Polaris PWC Knowledge;

    Some 650 and 750 Fuji engine models have a small metal flow restrictor (Polaris part number 5020773) inserted inside the return fuel line, about one inch from the last carburetor. It looks like a brass plug in the return fuel line, and it has a tiny hole driller through the center. The restrictor is used to boost fuel pressure inside the carburetors, and is in addition to the internal flow restriction in the Mikuni SBN carburetor.

    Nothing like in field testing, thanks for the help though.
    My apologies for not answering your original question. In all the reading and discussions I have seen, I do not recall anyone testing and confirming that replacement of the 750s stock pump with the pentagon pump will allow you to eliminate the in line restrictor. My knowledge comes from the same location as yours, and it has been drilled into my brain to install the restrictor, except on 780 carbs which have a pre-installed restrictor in the return nipple in addition to any other internal restrictors.

    Happy testing and please report back the results!!!

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